Aquatic facilities such as swimming pools and spas have become increasingly popular in private homes, hotels, fitness centers, and resorts. To ensure that the aquatic facilities can be enjoyed safely, the water must be treated to reduce or eliminate chemical oxygen demands (COD) and/or total organic carbon (TOC). When the COD and/or TOC increases in the water, the oxidation reduction potential of the water decreases and oxidizers are added to maintain a healthy level of oxidation reduction potential. A common oxidizer that is used in aquatic facilities is chlorine or bromine. However, when chlorine or bromine is present in the water above a certain level in the presence of COD and/or TOC, trihalomethanes (THM) and chloramines form in the water undesirably.
Common ingredients for treating water systems include various persulfate salts and persulfate donors such as potassium monopersulfate (PMPS), which is typically available in the form of a triple salt, (KHSO5)x.(KHSO4)y.(K2SO4)z (herein referred to as “PMPS triple salt”). However, persulfate salts, such as potassium persulfate (K2S2O8), are difficult to use because they cause severe irritation to facility users (e.g., swimmers, bathers) at concentrations above about 2 ppm. The strong oxidation potential of PMPS triple salt makes it effective for decreasing the concentration of COD. Typically, these chemicals are applied to the aquatic facility through a “shock treatment” whereby the facility is evacuated and the product is broadcast across the water surface. The facility users may not be allowed to come in contact with the treated water for a period of time after the treatment due to concerns for irritation.
PMPS usually contains potassium persulfate (K2S2O8) as a result of being prepared using oleum. Persulfates have a long halflife in aquatic water facilities and are undesirable. As a result of the concerns for irritation resulting from accumulation of persulfate, PMPS can be used only at limited dosages, which typically do not exceed two pounds per 10,000 gallons of water per week.
While PMPS maintains the water quality in aquatic facilities reasonably well, it is not convenient to use because of the need to evacuate the facility during use and the fact that it can only be used in limited doses regardless of how heavily the facility is used. Thus, a way of cleaning the water without these inconvenient limitations is desired.